Method of obtaining rubber from cryptostegia



Patented July 11, 1944 METHOD OF OBTAINING RUBBER FROM CRYPTOSTEGIA John McGavack, Leonia, N. J., as signor to United States Rubber Company, corporation of New Jersey Application September 1, 1942, Serial No. 456,967

. N Draw New York, N. Y., a 1

Claims (Q1. 47-10) This invention relates to a method of obtaining rubber from plants of the genus Cryptostegia, such as Cryptostegia madagascariensis, Cryptostegia grandiflom, and the hybrid of these two species.

At the present time rubber is commercially obtainedfrom plants, such a guayule,by mechanica-lly crushing and macerating the whole shrub in the presence of water, as by ball-milling the ground-unplant, whereupon the rubber becomes agglomerated and separates from the. remaining portions of theplant by floating on thewaten The rubber content of Cryptostegia is very seldom more than 1% to 1 /2% when the.

whole plant is considered, as against to, 20% rubber content inguayule. With such small rubber, content. of Cryptostegia, itis not commercially feasible to apply the ball-milling re-' coveryprocess by which rubber is obtained from guayule- 'It'has been previously suggested that rubber-containing plants be disintegrated by grinding orother methods,. and'the woody por-' tion separated by filtering, classifying, air-blowink, or the like, so that the remainder of the plant whichtcontains most of the rubber can be more successfully processed by a mechanical disintegration in water. By such methods, it is possible to remove at the most 40 to 50% of the woody material, and hence the concentration of rubber in the Cryptostegia so processed could be not much more than 2%, which is still too low a figure to deal with commercially in a mechanical disintegration recovery process. Furthermore, such a method is not particularly applicable to Cryptostegia as there are two rubber-bearing sections of this plant, the bark section and the pith section, and it is extremely difiicult to make any mechanical separation of these parts, so that all of the bark and all of the pith containing the rubber portion are removed from the woody fraction.

I have discovered a method of obtaining rubber from Cryptostegia which is quick and economical and which in effect increases the proportion of rubber sufiiciently in the parts of the plant to be treated so that these plant portions may be commercially mechanically crushed and macerated in the presence of water, as by ball-milling, to recover by flotation the agglomerated rubber in a manner similar to the recovery of rubber from guayule.

In carrying out my process for obtaining rubber from Cryptostegia, the ends of the plants are clipped off a short distance, for example, about to rest, and then the plants are clipped: back a short distance from. the "DrBViOlISIy cut ends, for example',about /4" to /g'fl- 'This-resting and cut ting maybe repeated any desired number of times with varying restperiods from a few hours toone or more days, 'depen'ding on thetotal numberof- Y A." to /2" on the first day, the plant is permitted clippings "that have beenfmadef' The restingof the plantfafter clipping gives time for thelatex-q to flow to the cut end and. flow out or bleedJSome of the latex will flow "down' the "surface of the plant. In this manner the rubber will be yconcentrated very closeto the cut ends and the subsequently-clipped sections will :have sufficiently' high rubbercontentto permit eifective mechanical recovery of the rubber without 'difliculty; In extracting the rubber from the clipped sections, the sections may be partially dried, disintegrated' withany grindingmachine, andthen' ball-milled in water, usually for six to sixteen hours-after which the rubber agglomerates in ballsor clotswhich "float to thesurface -and may be skimmed' off and dried. It is 'sometimes desirable to add a small amount of fixed alkali to the water in' the ball-milling procedure. The' original clipped end sections with the normal rubber content of around 1% maybe mixed with the subsequently cut sec'-' tions of considerably"higher c'ontent in the me chanical rubber-extracting process, or the subsequently cut sections of higher rubber content may be used alone for extracting the rubber, discarding the original ends.

The followin examples illustrate the increased rubber content of the cuttings which are the result of the alternate resting periods and clippings of the present invention, the rubber contents of the various clippings being determined mechanically by ball-milling in water for sixteen hours:

Example I Four to six year old Cryptostegia plants were clipped each day for fourteen days, and it was found that the rubber content was considerably increased for the second, third, and fourth clippings after the original end had been cut oil and that even up to the thirteenth day the rubber content of the clippings was greater than the rubber content of the original plant, or original end clippings. The rubber content of the original clipping on the first day was 1%, whereas the rubber contents of the subsequent days were as follows: second day-14%, third day-l0%, fourth day- 4%, fifth day-1.5%, sixth day-2%, seventh day-2.5%, eighth day2%, ninth day-1.5%, tenth day-2%, eleventh day-4.5%, twelfth day-2%, thirteenth day2%, fourteenth day- 1%. r

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excellent sheet-ofrubber j I Example II In this case the plants were clipped on the first, third, sixth and eighth day to; give' longer periods of rest between clippings with a corre-L sponding greater increase in rubber content over, c an extended period of time. .'.In .this case the rubber content of the original cut ends, i. e. the

first day clippings, was .6%, the third day clip pings 9.5%,the sixth day clippings 3.'7%, andthe eighth day clippings 8.5%.

Example III In. this case the -.Cryptostegia plants were clipped three successive days andqthen rested four dayaandthen clipped three more days with the following; results:- They rubber content of the original clipped ends/ongth'e first day was 2%, the rubber content oi' the-l-clippings onthe second day was 11%, ,omthe thirdday 2%, on the seventh day 4%, on the eighth day 2%, and on theninth day 2%. .1 0

It mayz'beseenkfrom the above that'the percent'rubber in the cut ends of the plant may be substantially increased so that, therubber may be readily extracted -commerciallyr. from the clipped-sections in the conventional manner, of

extracting rubber from wild plants-andshrubs; such as guayule. The rubber 'of.course may also be extractedfrom the, clippings by solvent proc-. esses but such processes are not-as satisfactory as simply, crushing and ball-'millingwith'water. In any case,- the present invention'will' substantially increase the rubber; content of the? plant parts from which the :rubber is to be extracted so that regardless of the method of finally extracting the rubber,-- the new-method -of treatmentjgof the plants by resting andgclippingis a decided improvementover any prior suggestions for dealing with the Cryptostegia plant 1' v In View of the many changes and modifications that may be made without departing from the principles underlying the invention, reference should be made to the appended claims for an understanding of the scope of the protection atforded the invention. c

Having. thus described my invention; what I claim and desire to protect by Letters Patents is:

,1. Method of obtaining rubber from Cryptostegia which comprises clipping sections of the plant i a short distance from the ends, allowing the plant to rest, then clipping back a short distance from .the previously clipped ends, and extracting rubber, fro'r'nthe clipped sections.

'2. Methodof obtaining rubber from Cryptostegia which comprises clipping a short distance fro'n'r the endsof' sections of the plant which have previously been clipped allowing the plant to rest,

"1 thenclipping back a short distance from the thus clipped ends, and extracting rubber from the clipped sections. 5 a

"3. Method of obtaining rubber'from Cryptostegia which comprises clipping sections of the plant a short distance from the ends, allowing the plant to rest at least a day, then clipping back a short distancefrom the previously clipped ends, and extracting rubber from the clipped section's;

4. "Method of obtaining rubber from Cryptoste-' gia which comprises clipping sections of the plant a short distance from the ends, allowing the plant to rest until the concentration'of rubber in the remaining ends is substantially greater than the concentration of rubber in the clipped end sectionsythn' clipping back a short distance from the previously'clipped ends, and extracting rub her from the clipped sections. a g

- 5. Method of obtaining'rubber from 'Cryptoste gia'which comprises clipping'sections of theplant' a shortdistance from-the ends, allowing the plant to rest, then clipping back a short distance from the previously clipped ends, and mechanically extracting the rubber from the clipped sections by macerating in an aqueous medium. r

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